Spindle shaft with intermediate ball bearing



J. 0. WILSON Filed Oct. 20 1945 Dec 18, 1945.

'sPIND E SHAFT WITH INTERMEDIATE BALL BEARING l WW I. 7 EH :5 m v a Q. EI E H. I A E m,

Patented Dec. 18 1945 assists I SPINDLESHAFT. m'rn in'rE Em T -l T A IBALLBEARING v John 0. wilsom springfield; amt, assigrior to The Thompson,Grinder Company Ohio, a corporation of Ohio; i

pringfleld, f

- Application October 2o,194.3,;seria1 0. 5 e927: sfclaim's. .(Cl .51--16 6 The present invention relates to precision working tools and,more particularly, to machines for cutting, abrading, ,or finishingsurfaces wherein a precision of dimension, spacworking with ordinarytolerances allowed, and

(3) high precision machines in which the tolerances are practicallyzero. In the first group of machines may be placed certain types ofheavy boring mills while the second type of machine may includepractically all of the lathes, drill presses, shapers and rough planers.The present invention is concerned with the third group of thesemachines in which the requirements of precision working are so high asto place machines of this character in a class distinctly separate fromall other types of metal working machines. These high precision machinesare constituted almost entirely of grinders and the character of thework is to grind perfectly, flat surfaces to extremely close tolerances.

Many problems arise in connection with high precision grinders that arenot present in connection with other'machines in that the slightestmisalignment of the rotating parts, including the shaft; the slightestchattering of the grinding wheel or the slightest wear at the bearingswill definitely prevent such machine from performing its highlyspecialized and critical task. Considerable development work has beenundertaken by the various manufacturers of precision grinders with aview to improving the character ofthe bearings so as readily andaccurately to tighten up on the slightest wear, and careful attentionhas been paid to the matter of adjusting the thrust of the wheel. Buteven with the precautions brought about, by this high state of 1development and research, minute movements of the wheel were stillpresent which, while not being detectable by the eye nevertheless gaverise to imperfections in the finished surface such as to precludeunqualified acceptance .of

the work. 7 I

The primary object of the invention is to provide a grinding machine ofthe high precisional type in which the grinding wheel is caused to runabsolutely true both in the radial and longitudinal directions in orderthat surfaces may be ground to the smallest allowable tolerances. Thisobject is carried out in brief by extending the length .of the grinderspindle, then. journalling the .ends of the shaft improper bearings sothat any slight misalignment of the bearing remote from the grindingwheel can havefllittle'or no effect on the rotational conditionsi'ofthat portion of the shaft which is immediately adjacent the grindingwheel. The

added length of the shaft permits the interposition'of thedrivingmotor'between the bearings and any 'whip' that is caused by therotating parts" offthe motor is accommodated and completely prevented bythe use of intermediate bearings positioned near the motor. By placingthe motor'intermediate the ends of the shaft no strains are set upwithin the shaft notwithstanding its considerable length and yet nowhipping or otherfmechanical distorting effects are introduced anywherealongthe shaft.

' The invention will be better understood when referenceis'madc to thefollowing description and the-accompanying drawing which shows inlongitudinal cross section the improved structure by'which a highprecision grinding wheel canb'e satisfactorily'mount'ed. Referencecharacter I designates a metal casting whichmay constitute part ofthemain frame of the "machine." This casting is cored to leave severalinwardly extending flanges 2, 3 in which the -=flange 2 carries alongitudinally extending {any large cylindrical -metal casing 5 which isthe tubular hub- 4.

connected at its inner end as indicated at 6 with A plurality of spacedstrengthening ribs 1 maybe provided between the flanges or walls 2, 3and secured along the outer edges to the frame I and at the inner edgesto the tubular hub 44 The casing 5 is normally 'open' and terminates inthickened portion 8. This end portion serves as a seat for a combinedcover and hub or sleeve member 9 which contains the outer bearing. Amulti-shouldered shaft in is carried at its outer'end within the hub orsleeve member 3 by two sets of ball bearingslseparated by-a spacersleeve [2. The end of the shaft is threaded as indicated at [3 toreceive a nut I 4 which abuts the outer surface of the right handballbearing element I I. A cap 'l5'is screwed as indicated at It, or in anyother manner secured to the hub 9. The left hand set of ball bearings ,Hare held in position by means of a screwed plate I]. which contains anannular groove ill for rotatably receiving the flange extensionfof acollar l 9 is set-screwed to the shaft asindicated'at -M; To the left ofthe bearing motor. The armature of the motor is indicated at 22 and thefield at 23, this armature abutting a heavy hub piece 24. The field ofthe motor is secured to the cylinder by means of screws 25 and thearmature of the motor is keyed to the shaft as indicated at 26.

The grinding wheel end of the shaft Ill is journalled in an ordinarytapered sleeve bearing, the sleeve being designated at 21. Immediatelysurrounding the sleeve there is a liner which fits snugly within thetubular housingJ. This liner may be pinned or otherwise secured to thehousing to prevent rotation. The sleeve 21 is threaded at the left handend as indicated at 29 for receiving a cylindrical nut 30 which servesto move the sleeve 2! longitudinally with respect to the shaft. Thesleeve is of a split character so that a movement to the right willcause a tighter fit between both halves of the sleeve and the shaft.

The shaft I0 is provided at its grinding wheel end with a taperedportion indicated at 3! into which is keyed a wheel backing plate 32 ofany suitable and well known type. The backing plate is provided with agroove 33 which is adapted to receive an annular extension 34 on thecylindrical nut 29, The backing member 32 is provided with a pair ofstep-down shoulders indicated at 35 and 36 respectively, the former ofwhich serves as a seat for a grinding wheel 31. The latter is shoulderedas indicated at 38, this shoulder being in line with the shoulder formedbetween the two step-down portions of the backing plate 32. so as torovide an annular recess for receiving a clamp ring 39. The interiorbore of the ring is thread ed at at to engage threads on the shoulder36. The backing member 32 is provided with a circular ledge 4| againstwhich the wheel may be cause to hear when the clamp ring is screwed onthe backing plate.

It is apparent from the drawing that the shaft I0 is of considerablelength in order to provide a long overhanging effect between the wheel31 and certain parts of the frame member. The heavy armature 22 of themotor is carried by the shaft and it is evident that there may be aconsiderable whipping effect at the middle of the shaft due to its longlength. This effect obviously causes undue wear at the sleeve bearing 21and eventual wobble of the wheel 31 with consequent poor quality ofwork. In extreme cases the sleeve bearing might be seriously damagedunder these circumstances calling for an early eplacement thereof. Inorder to avoid the possibility of a whip ing action, the prior art hasconsistently avoided placing the motor at a position intermediate thebearings, but instead, the shaft ID has been extended beyond the righthand bearing and a coupling, usually of a flexible character, isattached to the driving motor.

In accordance with the principles of the present invention an improvedsupport structure is provided which permits positioning of the drivingmotor between the bearings and still prevents any whipping or otherdistortional effects on the grinding wheel due to this motor position.The improved structure includes an additional journal of the ballbearing type so arranged that the support for the additional bearing maybe made integral with the support for the other bearings. Thus, thetubular hub 4 is extended to the right of the sleeve bearing Zlalmost asfar as the armature 22 of the motor. A cover plate 42 is screwed ontothe right hand, end of the tubular hru'b as indicated at 43. The plate42 is provided with an annular recess 44 for receiving an oil sealpacking which directly contacts with the shaft. The plate 42 provides awall against which a ball bearing device 45 may be ressed by means of asleeve 46 which is pinned as at 41 to the hub 4, The sleeve 46 has anouter diameter as snugly to fit the housing 4 and an inner diameterconsiderably greater than the diameter of the shaft as can be seen onthe drawing. The inner race of the ball bearing device 45 is secured inany suitable manner to the shaft while the outer race is held rigidly ina stationary position by the clamping effect exerted by the sleeve 46.

It is evident that the ball bearing device 45 is positioned quite closeto the heavy armature and provides "a good support therefor. By mountingthe ball bearing on an extension of the tubular housing 4 economy ofconstruction is effected since the bearing support may be cast integralwith the remainder of the frame. It is apparent that due to the improvedposition of the motor the latter is given considerable protectionagainst externally applied damage because the casing 5 serves as asubstantial shield, and yet the motor can be adequately cooled by thefan 2 l It will be understood that I desire to comprehend within myinvention such modifications as come within the scope of the claims andthe invention.

Having thus fully described my invention, what I claim as new and desireto secure by Letters Patent, is:

1. In a grinding machine, a frame, a shaft, main bearings carried bysaid frame and rotatably supporting said shaft adjacent the endsthereof, a grinding wheel fixed to one end of said shaft, a tubular hubintegral with said frame and loosely surrounding said shaft from thegrinding wheel and inwardly to a point approximately midway of saidshaft, a motor having its stator carried by said frame and having itsrotor fixed to said shaft externally of but loosely adjacent the innerend of said hub, an intermediate bearing mounted in the inner end ofsaid hub and rotatably supporting said shaft closely adjacent to saidrotor, and means positioned between the grinding wheel and hub fortightening the main bearing nearer to said wheel.

2. In a grinding machine, a frame, a tubular hub integral with saidframe, a casing integral with said frame having an axis coincidentalwith the axis of said hub and of larger size than said hub, said hub andeasing overlapping at their inner ends for a fraction of their lengths,a sleeve bearing mounted in the outer end of said hub and a ball bearingmounted in the casing remote from said sleeve bearing, a shaft rotatablymounted in said bearings, a grinding wheel on the end of saidshaftadjacent the outer end of said hub, a motor having its stator fixedin said casing and its rotor on said shaft, an intermediate bearingsupporting said shaft at the inner end of said hub closely adjacent saidrotor, and means whereby said sleeve bearing can be adjusted from theexterior of said casing while all the parts of the machine, includingthe grinding wheel, remain in position.

3. In a grinding machine, a frame, a tubular hub integral with saidframe, a casing integral with said frame having an axis coincidentalwith the axis of said hub and-of larger size than said hub, said hub andcasing overlapping at their iner ends for a fraction of their lengths, asleeve bearing mounted in the outer end of said hub and a ball bearingmounted in the oasirig remote from said sleeve bearing, a shaftrotatably mounted in said bearings, a grinding wheel on the end of saidshaft adjacent the outer end of said hub, a motor having its statorfixed in said casing and its rotor hub, said hub and casing overlappingat their inner ends for a fraction of their lengths, a sleeve bearingmounted in the outer end of said hub and a ball bearing mounted in thecasing remote from said sleeve bearing, a shaft rotatably mounted insaid bearings, a grinding wheel on the end of said shaft adjacent theouter end of said hub, a, motor having its stator fixed in said casingand its rotor on said shaft, an intermediate bearing supporting saidshaft at the inner end of said hub closely adjacent said rotor, andmeans mounted on said casing between the grinding wheel at the end ofsaid casing for tightening said sleeve bearing from the exterior of saidcasing while all the parts of the machine, including the grinding Wheel,remain in position.

5. In a grinding machine, a frame, a tubular hub integral with saidframe, a casing integral with said frame having an axis coincidentalwith the axis of said hub and of larger size than said hub, said hub andeasing overlapping at their inner ends for a fraction of their lengths,a sleeve bearing mounted in the outer end of said hub and a ball bearingmounted inthe casing remote from said sleeve bearing, a shaft rotatablymounted in said bearings, a grinding wheel on the end of said shaftadjacent the outer end of said hub, a motor having its stator fixed insaid casing and its rotor on said shaft, an intermediate bearingsupporting said shaft at the inner end of said hub closely adjacent saidrotor, means mounted on said casing between the grinding wheel at theend of said casing for tightening said sleeve hearing from the exteriorof said casing while all the parts of the machine, including thegrinding wheel, remain in position, a fan hub fixedly mounted on saidshaft adjacent said rotor and on the opposite side thereof relative tosaid intermediate bearing, and a fan fixedly mounted on said hub, saidintermediate bearing and said fan hub and said fan serving to preventlateral movement of said shaft.

JOHN 0. WILSON.

